Ugly looking text when drawing NSAttributedString in CGContext

Question

I want to display strings inside CoreAnimation layers, but unfortunately CATextLayer is not enough, mostly because it\'s difficult to use when using constraints and

Answer 1

I'm answering this because the coretext-dev archives are not searchable, and Aki Inoue from Apple just answered my question:

Since CALayer cannot represent subpixel color (aka font smoothing), you need to disable it. I believe CATextLayer does it by default.

Do CGContextSetShouldSmoothFonts(context, false).

Thanks, Aki!

Another comment by Milen Dzhumerov:

I don't believe this is accurate. We're drawing text into CALayers with subpixel anti-aliasing. You just have to make sure that you've drawn behind the text before drawing the text itself. See http://www.cocoabuilder.com/archive/message/cocoa/2008/3/28/202581 for references.

Milen is correct, in case you know the background colour beforehand, you can do:

CGContextSetRGBFillColor(ctx, r, g, b, a)
CGContextFillRect(ctx, (topLeft, size))
CGContextSetShouldSmoothFonts(ctx, True)

And you get pretty sub-pixel anti-aliased text. However, if you don't know the background colour, you need to turn off font smoothing or you'll get garbled results.